PROJECT SUMMARY/ABSTRACT Cigarette smoking remains a leading cause of preventable death in the United States, contributing to over 480,000 deaths each year. An estimated 8.6 million individuals live with chronic diseases caused by tobacco use, resulting in approximately $170 billion in direct medical costs, as well as $156 billion in lost productivity. Although significant strides have been made in the development of effective smoking cessation treatments, most established interventions are associated with high relapse rates. One avenue for increasing the effectiveness of smoking cessation interventions is to identify targets involved in phase-specific challenges and design focused, efficient, and rigorous experiments testing engagement of well-defined mechanistic targets. One key mechanism is subjective craving, which contributes to the maintenance of addiction and is also a risk factor for relapse. Pavlovian conditioning plays a role in craving among human smokers, who form strong associations between smoking and a variety of sensory cues. Among those who quit, memory traces of the rewarding properties of smoking endure and can be triggered by drug-associated cues even after prolonged abstinence. These associations can trigger strong cravings that increase the motivation to smoke and can lead to relapse. Thus, targeting drug-cue associations is key to the long-term impact on craving-induced relapse. Recent work in the Morikawa lab (consultant) tested pharmacologic augmentative strategies in rats using conditioned place preference (CPP), a Pavlovian learning model of cue-induced drug relapse. In a series of experiments, calcium channel blockage was identified as a key mechanism of action to enhance and prolong extinction of CPP. To translate these findings to humans, the current proposal will test isradipine, an FDA- approved calcium channel blocker, combined with cue exposure in an experimental therapeutics approach designed as an initial test of target engagement. To engage craving robustly in human participants, we will use multimodal smoking cues including innovative 360 video environments developed for this proposal and delivered through consumer virtual reality headsets. Adult smokers will be randomized to either: (1) cue exposure with isradipine (CE+ISR) or (2) cue exposure with placebo (CE+PBO). They will return 24-h later to repeat the procedure in a medication-free state. The target of engagement (subjective craving) will be measured after each of 10 trials during the two cue exposure sessions. The primary hypothesis will test whether isradipine enhances retention of craving extinction. A secondary exploratory aim will explore the feasibility and acceptability of implementation within a primary care setting where adult smokers receive healthcare. Findings will provide initial effect size data to determine whether target engagement is sufficient to warrant next stage research designed to evaluate the combined effect of isradipine and a cue exposure treatment on key clinical outcomes including smoking cessation and prolonged abstinence.